Cell C upgrades contract io cancelling

I canceled my CellC data device in mid May this year which mean my contract ended mid June. I have thrown the sim away already and today I noticed another Cell C data plan deduction from my account. I tried calling CellC 3 times to get this done. 2 5minute calls where customer service asks security questions and then transfers me to somebody who can help in Retention. But then I get this "The number you have failed does not exist"

Eventually managed to get hold of somebody in the retention departmemt who made me hold for 41mins just to tell me that I have had an upgrade done. And they will have to go review the calls.

Needless to say after using 60minutes of paying for my call with my airtime and having to rush to a meeting I had to drop the call and I am stil not sure who got a new contract on my name.

They did not bother to tell me they will investigate and get back to me. Who gives them the right to renew my contract when I clearly told them I am canceling because I signed already for a much better offer at a different service provider.